The present invention relates to a three-dimensional net made by warp knitting, particularly a three-dimensional net that is superior in structural stability and shape retainability in three-dimensional cords defining three-dimensional mesh spaces, press-load resistance and elasticity and that can be widely suitably used for various applications, and it also relates to a composite structural material using said net.
Following three-dimensional net is known as a net formed by double-web warp knitting. First and second webs at least one of which is of mesh construction are connected together by connecting yarns, so as to form three-dimensional cord portions which defining three-dimensional mesh spaces (mesh perforations penetrating the three-dimensional net), thus increasing the thickness and void content.
This three-dimensional net made by warp knitting has a direction dependency due to knitting construction including loop-forming configurations of connecting yarns, which is a drawback inherent in double-web knitted fabrics formed by warp knitting, with the result that the net is liable to collapse or fall in one direction (mainly in the knitting direction). Particularly, the larger the thickness of the net, the more distinct is said drawback.
In the case where the cord portions defining three-dimensional mesh spaces formed by double-web knitting constitute substantially vertical walls with respect to the front and back mesh webs due to double knit, the larger the thickness of the net, the greater the length of the connecting yarns (the height of the cord portions defining the three-dimensional mesh spaces), so that the stability against collapsing or falling is lost. To compensate for this drawback, it is necessary, for example, to increase web-wise dimension of the three-dimensional mesh spaces. That is, a three-dimensional net having an increased thickness necessarily has three-dimensional mesh spaces of increased dimension.
If, however, the three-dimensional mesh spaces is increased in size, the press-load-receiving area per unit area of the net becomes smaller and partialized, because the area for supporting external load is limited onto the three-dimensional cords. Thus, no sufficient pressure-resisting strength is achievable. Moreover, even if the surfaces is covered with sheeting, such as knitted or woven fabric, the regions corresponding to the three-dimensional mesh spaces are recessed, so that the surface presents net-peculiar undulations, which are unsightly and feel unpleasant to the touch. In addition, the pressure-resisting strength differs from place to place.
Therefore, it is far from satisfactory for use as a spacer, shoe insole, cushion material, mat material or the like that is desired to have a large thickness, sufficient elasticity and pressure resistance and to have three-dimensional mesh spaces of reduced size.
Further, in the case where high pressure resistance, high elasticity and high structural stability are required, the net thickness or the three-dimensional mesh space diameter (the distance across) cannot be made so large and the use of the net is limited. That is, it is impossible to provide a net whose mesh openings are large as a whole.
Further, in the case of articles of clothing, such as spacers for clothing, cushion materials or the like where substantial pressure resistance, elasticity and structural stability are required and where the three-dimensional mesh spaces are required to be small, the void content of a conventional three-dimensional net is low and grammage or weight (g) per unit area (m2) increases, a fact which is disadvantageous from the standpoint of use and cost.
Further, in order to allow a three-dimensional net made by warp knitting to be widely used for various applications in mat materials, cushion materials or the like, the applicant of the present invention has previously proposed a net designed to improve pressure resistance and structural stability (for example, (a) Japanese Registered Patent NO. 2762052, (b) JP-A-10131008(JP-A-1988-131008, Japanese Unexamined Patent Publication Hei 10-131008).
In the above, according to a document (a), yarns on the three-dimensional cords defining three-dimensional mesh spaces are alternately inclined right and left to form a truss structure. Meanwhile, according to a document (b), connecting yarns constituting three-dimensional cords defining three-dimensional mesh spaces are passed or extended in X-form to prevent collapsing or falling.
Heretofore, effort has been made to secure, by said techniques, structural stability for three-dimensional nets made by warp knitting. However, in either case, sufficient structural stability cannot be obtained unless a balance between the size of three-dimensional mesh spaces and the length of connecting yarns is achieved. Moreover, there are cases where the three-dimensional structure itself cannot be secured, and the void content lowers while the grammage (g/m2) increases.
For example, in the case of a net of truss construction in the document (a), if the thickness of the net increases, so does the diameter of three-dimensional mesh spaces, so that the strength to support a load in the direction of the thickness of the net is weakened, with the result that the pressure-resisting strength and elastic force in the direction of the thickness of the net are reduced. That is, in order to provide structural stability against collapsing or falling, it is necessary to increase the diameter of three-dimensional mesh spaces the more, the greater the thickness.
Further, in the case of the net of truss construction, the positions of the junctions of braids defining the mesh openings of front and back mesh webs are shifted in the knitting direction, so that a connecting yarn connecting a braid on first mesh web and corresponding braid on second mesh web is inclined rightward and leftward alternately. Thus, in plan view, the braid on the first mesh web crosses the braid on the second mesh web. Therefore, when the net is unfolded to be spread and subjected to a treatment such as heat setting, the distance between stitch forming positions of connecting yarns hung between the braids in the first and second mesh webs differs. The distance between which the connecting yarn are passed and hung become largest when the connecting yarns are passed and hung between junctions of the first and second mesh web, while the distance become smallest at the plan-view-wise crossing point.
On the other hand, since the length of the connecting yarns passed and hung between the front and back braids is basically constant, the connecting yarns are almost linear between said junctions between which the distance is largest, while in said crossing portion where the distance is smallest, the connecting yarns are bent, failing to develop sufficient pressure-resisting strength. Further, since the connecting yarns between said junctions are most greatly inclined, the pressure-resisting strength is lower than when the connecting yarns extend vertically.
Further, in a three-dimensional net of the type in which the front and back braids that are in zigzag form cross each other, there are connecting yarns that are upright with respect to the front and back mesh webs and connecting yarns that are inclined. The effect of these connecting yarns provides two strengths, the pressure-resisting strength and the strength to resist transverse collapsing or falling. If the number of upright connecting yarns is increased in order to increase the pressure-resisting strength, the strength to resist falling decreases. Reversely, if the number of inclined connecting yarns is increased in order to increase the strength to resist collapsing or falling, this results in a decrease in the pressure-resisting strength in the direction normal to the net surface (the direction of the net thickness.) Further, since a complete balance between the pressure-resisting strength in the direction of the net thickness and the strength to resist transverse falling cannot be achieved, stability with respect to pressure-resisting strength is insufficient.
Therefore, although the three-dimensional nets proposed in the documents (a) and (b) are intended to solve the problem of direction dependency countermeasures against collapsing of falling in the knitting direction peculiar to double-web knitted fabrics formed by warp knitting have not necessarily produced a sufficient effect in addition, in use of the proposed nets, problems have sometimes occurred in connection with press-load resistance. For this reason, certain limitations have been imposed on the size of three-dimensional mesh spaces and the length of connecting yarns and their applications and manner of use have been limited.
Accordingly, the present invention is intended to provide a three-dimensional net solving these problems, that is, a three-dimensional net that has the improved shape retainability of three-dimensional cords defining three-dimensional mesh spaces, particularly effective in canceling the direction dependency peculiar to warp knitting, superior in structural stability and pressure resistance, capable of retaining satisfactory elasticity and easily forming three-dimensional cords defining three-dimensional mesh spaces simply by imparting tension, said net having a high void content, being light in weight and easy to handle, these characteristics being utilized to use the net as an industrial material for various clothes, mats, cushions and their intermediate materials or use the net as a vegetation net on the faces of slopes or a protective net, the net being widely suitably used for various other applications, and the invention also provides a composite structural material using said three-dimensional net.
Invention-wise three-dimensional net which is formed by warp knitting and which has a first mesh web, a second mesh web and connecting yarns connecting the first and second mesh webs, on front and back sides of the net, with a required spacing therebetween; comprises three-dimensional cords each formed by braids on the first mesh web and the second mesh web and by the connecting yarns front-to-back-wise passed between the braids of the first and second mesh webs, said first mesh web having larger mesh openings than those of the second mesh web; wherein, at least partly in each of said three-dimensional cords, said connecting yarns are passed from a single braid on the first mesh web to a plurality of braids on the second mesh web so that said three-dimensional cord has a width of at least one mesh openings on the first mesh web.
According to this three-dimensional net, the mesh openings differ in size between the front and back mesh webs, and since one mesh is smaller than the other mesh, the use of the net, even if having the relatively large three-dimensional mesh spaces, with its smaller mesh openings turned frontward results in the front surface having an attractive appearance and a pleasant touch, and particularly in the state in which the net is covered with a sheet, there is no possibility of the unevenness of the net appearing on the outer surface. Further, since a combination of larger and smaller mesh openings provides relatively large three-dimensional mesh spaces, the void content is high, making it possible for the net to have a void content of, e.g., 80% or more, and the net can be made lightweight even if it is thick. Above all, those nets whose void content is 90% or above are further lighter in weight and easy to handle.
Further, since each of said three-dimensional cords defining three-dimensional mesh spaces has, in the whole or part thereof, said connecting yarns extended from a single braid on the side associated with the larger mesh openings to a plurality of braids on the side associated with the smaller mesh openings. Thus, the three-dimensional cord has a width of at least one mesh openings on the side associated with the smaller mesh openings. There are attained satisfactorily retained elasticity, satisfactory structural stability of the three-dimensional cords, suppressed direction dependency peculiars to double-web knitted fabrics made by warp knitting, no possibility of falling, and satisfactorily retained pressure resistance.
Further, since the mesh openings of one of the front and back mesh webs are smaller, it is easy to open and spread the folded net, the planar dimensional stability increases for the net in its entirety, and the three-dimensional shape stability and dimensional stability in the spread state are improved. Therefore, the size of the mesh openings on the front and back sides and of the three-dimensional mesh spaces can be freely selected according to uses.
Particularly, at least partly in each of said three-dimensional cords, said connecting yarns are inclined as front-to-back-wise passed between the first and second webs, so that said each of three-dimensional cords assume a three-dimensional shape having three-dimensional voids therein. The three-dimensional voids preferably are substantially triangular, substantially inverted triangular, substantially trapezoidal, substantially inverted trapezoidal or the like in cross section.
Thereby, the passed and hung portions of the connecting yarns inclined in said three-dimensional cards are inclined mainly to opposite sides as seen particularly from the braids on the side associated with larger mesh openings to perform a prop action. Therefore, the pressure resistance is satisfactory, the shape is hardly lost, the structural stability of the three-dimensional cords is superior, balance is kept, direction dependency peculiar to double-web knitted fabrics made by warp knitting is suppressed, and falling never occurs. Therefore, in the case where forces act substantially perpendicularly to the reticular front and back mesh webs; the three-dimensional net is compressed perpendicularly to the front and back surface, exerting an excellent cushioning property.
Further, in said three-dimensional net, it is preferable that each of said three-dimensional cords has a three-dimensional void defined by the inclined connecting yarns so that said three-dimensional cords form a tunnel structure continuous to be fluid-conductive in the knitting direction and/or in the knitting-width direction.
That is, when the three-dimensional cords thus formed are stretched by being opened or deployed as a three-dimensional net, three-dimensional shapes are formed that are continuous in tunnel form, so that the effect of stabilizing the three-dimensional shapes is high and said structural stability and the effect of preventing falling are further increased. Further, the voids in the three-dimensional cords continuous in tunnel form can be effectively utilized as passages for air, water and the like. For example, when the net is used as a vegetation net for greening or stabilizing the faces of slopes, satisfactory passage of air and water can be ensured since said three-dimensional cords possess tunnel-shaped three-dimensional voids therein even if the three-dimensional mesh spaces are filled with foreign substances, such as soil dressing.
If the net is used as a bedsore preventing mat, a sheet having an air conditioning function for automobiles, inner material or insole for shoes, or the like, sufficient air is supplied all the time not only by the tunnel construction of said three-dimensional voids but also by the high three-dimensional void content provided by the three-dimensional mesh spaces and by a pumping effect provided by the cushioning property of the net; thus, it can be suitably used as a mat material having good gas permeability.
Said three-dimensional net of the present invention may be made such that the braids forming the larger mesh openings in one of the front and back mesh webs are formed by a row or rows of stitches forming one wale or a plurality of wales, while the braids forming the smaller mesh openings in the other mesh web are formed by a row of stitches forming one wale or by rows of stitches forming less wales than in the braids forming the larger mesh openings, said braids being alternately junctioned together with the braids adjoining on opposite sides every required spacing in the knitting direction, thereby assuming a zigzag form, forming polygonal mesh openings.
Thereby, the connecting yarns in said three-dimensional cords are extended from the braids forming larger mesh openings or from junction between said braids to a plurality of the other braids as the connecting yarns are rightwardly and leftwardly inclined, thus forming three-dimensional shapes having three-dimensional voids therein as described above. Furthermore, this ensures satisfactory reliable prop action provided by said connecting yarns, good balance, and pressure-resisting strength and shape retainability further improved as a whole.
Further, said three-dimensional net of the present invention may be made such that the braids forming mesh openings in one of the front and back mesh webs are knitted in marquisette construction using a row of stitches that is a row of chain stitches forming one wale and inlay yarns traverse-wise inserted in said row of stitches, whereby the mesh openings of the mesh webs assume a quadrangular shape, while the braids forming mesh openings in the other mesh web are formed by a row of stitches forming one wale or by rows of stitches forming a plurality of wales, said braids being alternately junctioned together with the braids adjoining on opposite sides every required spacing in the knitting direction to assume a zigzag form, whereby the mesh openings of said mesh webs assume a polygonal shape.
In this case, the marquisette construction of one of the front and back mesh webs ensures that the net has a greater wale-wise and course-wise tensile strength and a superior wale-wise and course-wise dimensional stability and shape retainability, and satisfactorily retained pressure resistance. Therefore, the net can be suitably used particularly for applications where tensile strength is required.
Said three-dimensional net may be made such that in the knitting direction, the number of knitting courses for one or more larger mesh openings in one of the front and back mesh webs is equal to a plurality of times the number of knitting courses for one smaller mesh in the other mesh web, while in the knitting direction and in the knitting-width direction, one or more larger mesh openings in one of the front and back mesh webs correspond to a plurality of smaller mesh openings in the other mesh web which plurality is greater than the number of larger mesh openings.
In this way, a three-dimensional net of larger and smaller mesh openings on the front and back sides is easily produced by warp knitting, by freely setting sizes of the mesh openings on the front and back sides in accordance of usage.
In a preferred embodiment of the invention-wise three-dimensional net, in a plan view, at least one mesh opening on the second mesh web falls substantially in a middle portion of a larger mesh opening on the first mesh web, and connecting yarns being front-to-back-wise passed between the braids respectively defining said at least one mesh opening and said larger mesh opening in such a manner to surround entire peripheries of these mesh openings, so that the three-dimensional mesh spaces defined therein are substantially funnel-shaped.
In the three-dimensional net of such arrangement, the three-dimensional cords defining the three-dimensional mesh spaces have three-dimensional shape continuous in tunnel form and have three-dimensional voids that open with larger mesh openings. The three-dimensional voids are substantially triangular or the like in cross section, in such a manner to surround entire peripheries of these mesh openings. Thus, such arrangement makes a compressive load in the direction of the thickness to be distributed in a well-balanced manner, almost completely eliminating the direction dependency peculiar to double-web knitted fabrics, further improving the structural stability and pressure resistance.
In another preferred embodiment of the invention-wise three-dimensional net, in a plan view, junctions of braids on the second mesh web fall substantially on junctions of braids and middle portions of mesh openings on the first mesh web; and the invention-wise three-dimensional net comprises: vertical connecting yarns each passed between a junction on the first mesh web and a coincided junction on the second mesh web and inclined connecting yarns each passed between a junction on the first mesh web and rightward and leftward adjacent junctions on the second mesh web, each of said adjacent junctions falling substantially in a middle portion of a larger mesh opening on the first mesh web in a plan view.
Thus, the junction on the side associated with larger mesh openings has the Vertical connecting yarns and the connecting yarns rightwardly and leftwardly inclined, securing sufficient pressure resistance, preventing collapsing or falling, and also improving structural stability.
In another preferred embodiment of the invention-wise three-dimensional net, at discretionary positions in the knitting direction in the three-dimensional cords, each of the connecting yarns are passed from a first row of stitch on the first mesh web to a second row of stitch on the second mesh web, said second row of stitch being shifted rightward or leftward by at least one wale from a row of stitch coincided with the first row of stitch, thereby connecting yarns crossing each other in substantially X-form in the three-dimensional cords or three-dimensional mesh spaces. Thereby, the shape retainability of the three-dimensional cords is further improved, falling never occurs, and satisfactory cushioning property is retained in a direction perpendicular to the front and back surfaces, so that satisfactory pressure-resisting strength that is substantially uniform throughout the net can be retained.
In a still another preferred embodiment of the invention-wise three-dimensional net, at required places in the knitting direction, the size and/or shape of the mesh openings in the front and back mesh webs is varied. Thus, partly varying the size or shape of the mesh openings in the front and back mesh webs improves balance with respect to a compressive load in the direction of the thickness, suppresses the direction dependency peculiar to double-web knitted fabrics made by warp knitting, and further improves wale-wide and course-wise dimensional stability, structural stability, pressure resistance, etc. Further, it is also possible to provide aesthetic variations.
Said three-dimensional net of the present invention may have devoid portions devoid of the connecting yarns between front and back braids that are formed in discretionary positions in a knitting direction at each of the three-dimensional cords and/or at discretionary one(s) of the three-dimensional cords arranged in a knitting-width direction, in such a manner said devoid portions facilitate communication in the knitting direction and/or in the knitting-width direction.
According to this three-dimensional net, since the space portions having no connecting yarns in the three-dimensional cords define three-dimensional spaces substantially linearly communicating with each other in the knitting direction and/or in the knitting-width direction, it is possible to insert in said space portions long objects having various functions, such as members for connection to other members or for stretching of the net, particularly it is possible to insert said long objects crosswise. Thereby, the net can be suitably used as a composite material having functions according to uses.
Said three-dimensional net of the present invention may be arranged such that in selvages on both ends in a knitting-width direction, at least one of the connecting yarns is omitted so as to form a sleeve continuous in the knitting direction. Thereby, members for adhesion or sewing for joining to other members or long-sized members for stretching or attaching the net can be inserted in the sleeve portions at the selvages on the opposite ends. The sleeve portions may be flattened and utilized for joining to other nets or sheets.
An invention-wise composite structural material is formed by stacking a plurality of three-dimensional nets according to any one of the above arrangements.
According to such composite structural material, stacking a plurality of three-dimensional nets ensures that the mesh web openings of two mutually abutting nets mutually act to control their deformation and direction dependency peculiar to double-web knitted fabrics, and that the abutting portions of the mesh webs serve as reinforcing layers in the intermediate region in the direction of the thickness, so that even if the thickness is considerably great, the shape retainability, structural stability and pressure resistance can be retained in a very satisfactory state as a whole. Further, for example, stacking mesh webs with their sides having larger mesh openings facing each other provides a structural material having an increased void content and smaller mesh openings appearing on the front and back sides. Further, by combining nets respectively having higher and lower degree of elasticity, it is possible to eliminate the feeling of touching the bottom with respect to pressing in the direction of the thickness. Therefore, this combination can be suitably used for various applications in which, for example, cushion materials mat materials, shock absorbers and other three-dimensional net structures can be used.
In said composite structural material, a plurality of three-dimensional nets constructed to be different in knitting gauge, yarn thickness and mesh size can be stacked. In this case also, it is possible to obtain composite structural materials having strength, elasticity and net mesh construction suited for respective uses.
Further, another composite structural material of the present invention is made by stacking any one of the three-dimensional nets of above-described construction and a net of another construction. In this case also, the shape retainability and structural stability of the three-dimensional nets are increased and this material can be suitably used for various applications that make use of the void retainability, elasticity and pressure resistance provided by the three-dimensional construction.
Another invention-wise composite structural material comprises a flat stuff selected from a group consisting of a knit fabric, a woven fabric, a pile fabric, a nonwoven fabric, a sheet of cottony fluff material, a sheet of urethane foam, a synthetic resin film, a paper and other sheet; a synthetic resin plate, a wood plate, a metal plate, and other plate; and a mat-shaped cushion stuff containing air, water or oil therein; said flat stuff being placed on and adhered to at least one of the front and back sides of the three-dimensional net and/or between the three-dimensional nets.
By this feature, the pressure resistance and structural stability of the three-dimensional net are improved. By utilizing each flat stuff and respective imparted property, the three-dimensional net may be used as a mat stuff, a cushion structural wall material or heat insulator or the likes
Still another invention-wise composite structural material comprises gas-impermeable sheets or gas-permeable sheets being stuck on the front and back sides of the three-dimensional net to cover the latter; and at least one selected from a group consisting of gas, liquid, powder, a mixture thereof, and solid particles, which is enclosed or filled within the three-dimensional net. Thereby, the elasticity and pressure resistance possessed by the three-dimensional net, coupled with the deformability of the substance enclosed or filled therein, enables the composite structural material to be suitably utilized for beds, pillows and other bedding articles, chairs, sofas, shoe insoles, etc.